JP5892008B2 - Ball end mill and manufacturing method thereof - Google Patents

Description

  The present invention relates to a small-diameter ball end mill for milling precision molds and the like and a method for manufacturing the same.

The ball end mill has a cutting edge portion constituted by a side blade (outer peripheral blade) formed on the outer peripheral portion and a bottom blade formed in a spherical shape at the tip of the end mill. The ball end mill is used for surface processing of a workpiece such as steel or cast iron, and is mainly used for cutting a curved surface. Further, the R-surface machining of the corner portion where the vertical surface and the horizontal surface intersect can be performed by the spherical bottom blade.
In the processing of the cutting edge part of such a ball end mill, the shape is generally formed by cutting using a grindstone. For example, in the processing step, first, a gash and a rake face are processed in a cylindrical material, then a relief surface is formed on the outer peripheral surface subjected to outer diameter processing, and finally a cutting edge portion is formed.
In the end mill machined in this way, for example, as disclosed in Patent Document 1 and Patent Document 2, flank faces are formed in multiple stages with flank angles such as second and third angles. And the flank formed in multiple stages is processed by grinding with a grindstone according to each relief angle.

JP 2010-162677 A JP 2012-6134 A

  However, forming a flank having multiple flank angles complicates the manufacturing process. Further, the end mill in which such a flank is formed has a problem that chips are caught at the joint portion of each clearance angle when the workpiece is processed, and it is difficult to smoothly discharge the end mill.

  The present invention has been made in view of such circumstances, and a ball end mill capable of simplifying the manufacturing process of the end mill and smoothly discharging chips during the cutting of the workpiece, and the manufacturing thereof. It aims to provide a method.

  The ball end mill of the present invention comprises a tool tip rotated around an axis, a side blade disposed on the outer periphery of the tool tip, and an arcuate ball blade disposed at the tip of the tool tip. A pair of cutting edge portions are formed on opposite sides of the axis, and an outer peripheral portion of the tool tip is formed by an ellipse column formed by an ellipse around the axis, and the tip of the ellipse column And a tip ball portion formed by a rotating ellipse shape having a short axis of the ellipse as a rotation axis, and the cutting blade portion has the side blades at both ends of the long diameter of the ellipse at the axis. The ball blade is disposed on the surface of the tip ball portion from the tip of the side blade inward along the major axis direction of the ellipse, and the ellipse has a major axis of 2 mm or less and a major axis The ratio of minor axis to is set to 0.95 or less And wherein the are.

The outer peripheral portion of the tool tip portion is formed by an elliptical column portion and a tip ball portion, and the outer diameter of the cutting edge portion is set to the major axis of the ellipse. As described above, since the side blade and the ball blade are formed on the outermost peripheral portion of the ellipse, when processing the workpiece, the side blade and the ball blade first contact the workpiece, and the side blade and the ball blade The outer peripheral surface that follows is a flank so as not to come into contact with the workpiece. For this reason, it is not necessary to process the flank separately from the outer diameter processing, and the manufacturing process can be simplified.
Moreover, since the outer peripheral part formed in the ellipse is formed with the smooth curved surface without a joint, the chip | tip produced at the time of cutting can be discharged | emitted smoothly along the curved surface of an outer peripheral part. Moreover, since chips can be discharged smoothly, cutting resistance can be reduced, and stable cutting performance with a long life can be obtained.

Further, since the ratio of the minor axis to the major axis of the ellipse becomes closer to 1 as the shape of the outer peripheral part approaches a perfect circle, when the ratio is set to exceed 0.95, the ball end mill and the workpiece are processed. Non-critical contact with the object increases the cutting resistance. Therefore, it is set to 0.95 or less.
Note that the smaller the ratio, the more critically the ball end mill and workpiece will be in contact, but the thickness of the blade that acts as the cutting edge of the end mill becomes thinner, making it difficult to ensure strength. Is preferably set according to the required strength.

  The ball end mill manufacturing method of the present invention includes an elliptical column processing step for forming an elliptical column portion on a cylindrical material, a tip ball processing step for forming a tip ball portion on the columnar material, the elliptical column processing step and the tip The cylindrical material after the ball processing step has a cutting edge processing step for forming a gash and a rake face and forming a side blade and a ball blade, and the elliptical column processing step and the tip ball processing step are the cylindrical shape While the material is rotated around its axis, the cylindrical material is irradiated with a laser beam from the tangential direction of the elliptical shape, and the laser beam is irradiated in accordance with the rotational phase of the elliptical shape that moves with the rotation. The position is moved.

By forming an elliptical outer peripheral portion in the columnar material, it is possible to simultaneously form an outer peripheral portion that functions as a flank of the tool tip portion, and a side blade and a ball blade that are disposed on the outer periphery of the tool tip portion. Therefore, it is not necessary to provide a process of processing the flank, side blades, and ball blades separately from the process of processing the outer peripheral portion, and the manufacturing process can be simplified.
In addition, the side blade and ball blade machining process can be performed by rotating the shank with the cylindrical material attached while synchronizing the rotation phase and the irradiation position of the laser beam. It can be easily processed.
Furthermore, a high-hardness material such as a cBN sintered body, sintered diamond, cemented carbide or the like is used as a material for a small-diameter end mill used for precision cutting applications. For this reason, when the relief part is formed by grinding, it is difficult to machine with the desired accuracy by bending the grindstone strongly, but the entire tool tip is formed by laser machining without applying mechanical load. Therefore, it is possible to prevent a decrease in processing accuracy due to deflection or the like caused by processing with a conventional grindstone.
Further, the tool tip portion is formed with a smooth flank in a spheroid shape with, for example, Rz (maximum height) ≦ 1 μm by laser processing, so that the ball blade can be formed with a sharp ridgeline. Furthermore, the flank is also smoothly processed into an elliptical column just below the base of the tool than the ball blade, so that the side blade can be formed with a sharp ridgeline, and a sharp end ball end mill is manufactured. be able to.

  According to the present invention, by forming the outer periphery of the tool tip in an elliptical shape, chips can be discharged smoothly during the cutting of the workpiece, and the manufacturing process of the ball end mill can be simplified. Can do. Further, the tool tip portion is formed with a smooth flank in a spheroid shape with, for example, Rz (maximum height) ≦ 1 μm by laser processing, so that the ball blade can be formed with a sharp ridgeline. Furthermore, the flank surface is similarly processed smoothly into an elliptical cylinder just below the base of the tool than the ball blade, so that the side blade can be formed with a sharp ridgeline, and a sharp-cut ball end mill is manufactured. be able to.

It is the schematic of the tool front-end | tip part which shows one Embodiment of the ball end mill which concerns on this invention, (a) is a perspective view, (b) is a front view, (c) is a side view. It is a whole block diagram which shows the laser processing apparatus used for the manufacturing method of the ball end mill which concerns on this invention. It is a figure explaining the ellipse processing process of an outer peripheral part, and is the figure seen from the axial direction. FIG. 4 is a view seen from an arrow A shown in FIG. 3. It is a graph which shows the relationship between a laser beam irradiation position and the locus | trajectory of an elliptical contact, and a rotation angle. It is the schematic of a ball end mill.

Hereinafter, an embodiment of a ball end mill and a manufacturing method thereof according to the present invention will be described.
As shown in FIG. 1, the ball end mill 1 of this embodiment shown in FIG. 6 has a pair of cutting blade portions 11 formed on opposite sides of the axis x on the tool tip 2 rotated about the axis x. This is a two-blade ball end mill. The ball end mill 1 is configured such that a tip end of a cylindrical shank portion 3 is formed with a small diameter, and a substantially circumferential tip portion 5 is joined to the tip of a neck portion 4 with a small diameter. The tip portion 5 includes a cemented carbide portion 6 joined to the neck portion 4 and a tool tip portion such as a cBN sintered body and a diamond sintered body that are connected to the cemented carbide portion 6 to form a cutting edge portion 11. 2 and.

The outer peripheral portion 21 of the tool tip portion 2 is provided continuously with an elliptical column portion 31 formed by an ellipse around the axis x and the tip of the elliptical column portion 31, and rotates with the minor axis a of the ellipse as the rotation axis. The ellipse is formed by a tip ball portion 32, and the ellipse has a major axis b of 2 mm or less and a ratio of the minor axis a to the major axis b of 0.95 or less.
Further, the cutting edge portion 11 is formed by a side blade 12 disposed on the outer periphery of the tool tip portion 2 and an arc-shaped ball blade 13 disposed at the tip of the tool tip portion 2. The side blades 12 are disposed along the axis line x at both ends of the ellipse major axis b. Further, the ball blade 13 is disposed on the surface of the tip ball portion 32 from the tip of the side blade 12 inwardly along the direction of the major axis b of the ellipse, and is formed in an arc shape having a radius R = b / 2. And a pair of cutting blade part 11 is arrange | positioned in the position 180 degree apart in the circumferential direction. In addition, the code | symbol 15 of FIG. 1 has shown the gouache and the rake face.

As shown in FIGS. 2 to 4, the ball end mill 1 configured as described above is formed in a shape by irradiating a cylindrical material 20 forming the tool tip 2 with a laser beam (laser light) L.
As shown in FIG. 2, the laser processing apparatus 100 used in the manufacturing method of the present embodiment is an apparatus that performs three-dimensional processing by irradiating a columnar material 20 processed on the tool tip 2 with a laser beam L. This laser processing apparatus 100 holds a laser beam irradiation mechanism 22 that scans while irradiating a cylindrical material 20 with a constant repetition frequency by oscillating a laser beam L, and a shank portion 3 to which a chip portion 5 is bonded. , A rotation mechanism 23 such as a motor that can rotate, a moving mechanism 24 that is installed and can move in the xyz-axis direction, and a control unit 25 that controls them.

  The moving mechanism 24 includes an x-axis stage unit 24x that moves in the x-direction parallel to the horizontal plane, and a y-axis that is provided on the x-axis stage unit 24x and is movable in the y-direction perpendicular to the x-direction and parallel to the horizontal plane. The stage portion 24y and the z-axis stage portion 24z provided on the y-axis stage portion 24y and having the rotation mechanism 23 fixed to hold the shank portion 3 and movable in the direction perpendicular to the horizontal plane. Yes. Further, for example, stepping motors are used as the drive units of the stage units 24x to 24y, and the phase can be fed back by an encoder.

The laser beam irradiation mechanism 22 includes a laser light source 26 having an optical system that oscillates a laser beam to be a laser beam L by a Q switch and collects the laser beam in a spot shape, and a galvano scanner 27 that scans the laser beam L to be irradiated. I have.
As the laser light source 26, a light source capable of irradiating laser light with a short wavelength of 190 nm to 550 nm can be used. For example, in this embodiment, a laser light source that can oscillate and emit laser light with a wavelength of 355 nm is used. Further, the galvano scanner 27 is disposed directly above the moving mechanism 24.

A method for manufacturing the ball end mill 1 using the laser processing apparatus 100 configured as described above will be described.
First, the cylindrical material 20 is subjected to outer diameter processing for processing the elliptical column portion 31 of the outer peripheral portion 21 into an ellipse (ellipse column processing step). As shown in FIG. 3, in the elliptical column machining step, the cylindrical material 20 is rotated around the axis x, and the laser beam L is applied to the cylindrical material 20 in the tangential direction of the elliptical shape e (the outer peripheral shape after processing). And the irradiation position (focus position s) of the laser beam L is moved in accordance with the rotational phase of the elliptical shape e that moves with the rotation.
The locus of the rotational phase of the elliptical shape e can be obtained by reading the phase of the rotary shaft (axis line x) of the rotary shaft motor by reading the encoder signal of the rotary shaft motor. Then, by controlling the focal position s of the laser beam L in accordance with the rotational phase of the elliptical shape e, the elliptical column part 31 can be processed on the outer peripheral part 21.

  In the laser processing apparatus 100, the laser beam L is irradiated from the vertical direction (z-axis direction), and as shown in FIGS. 3 and 4, the focal point of the laser beam L along the locus of the elliptical shape e. Scan position s. In the rotational phase shown in FIG. 3A, the minor axis a of the y-axis and the elliptical shape e coincides, and the contact point between the laser beam L and the elliptical shape e, that is, the focal position s of the laser beam L is on the y-axis. Placed in. 3 (a), when the rotational phase of the elliptical shape e is rotated by 45 °, the locus of the elliptical shape e moves outward in the radial direction as shown in FIG. Are also moved radially outward. Thus, the focal position s of the laser beam L is arranged most radially inward when it coincides with the minor axis a of the elliptical shape e, and is arranged most radially outward when it coincides with the major axis b. The

  In the present embodiment, the focal position s of the laser beam L indicates the position of the beam waist. When the focal depth of the laser beam L is deep and the contact point between the elliptical shape e and the laser beam L irradiated from the vertical direction is within the focal depth range, the laser beam L is in the horizontal plane (x-axis and y-axis directions). The elliptical processing of the outer peripheral portion 21 can be performed by moving at. On the other hand, when the focal depth is shallow, the contact point between the elliptical shape e and the laser beam L is out of the focal depth range, so the position of the z-axis stage unit 24z is adjusted so that the contact point is within the focal depth range. To do.

  For example, the graph shown in FIG. 5 shows the locus of the contact point between the irradiation position (focus position s) of the laser beam L and the elliptical shape e when an elliptical shape having a minor axis a of 600 μm and a major axis of 1000 μm is processed. . In this case, the focal position s of the laser beam L is scanned between the radial position (300 μm) of the minor axis “a” of the y axis and the radial position (500 μm) of the major axis “b”, and the z position of the cylindrical material 20 is also adjusted. Is done.

In this manner, by performing a plurality of rotations of the cylindrical material 20 and scanning of the laser beam L, the elliptical elliptical column part 31 along the elliptical shape e is formed. The cylindrical material 20 subjected to the outer diameter processing is subjected to processing of the tip ball portion 32 (tip ball processing step), and an elliptic column portion 31 formed by an ellipse around the axis x, and the elliptic column. An outer peripheral portion 21 is formed which includes a tip ball portion 32 provided continuously with the tip of the portion 31 and formed in a spheroidal shape.
In the tip ball processing step, the cylindrical material 20 is irradiated with the laser beam L from the tangential direction of the outer peripheral shape after processing in a state in which the cylindrical material 20 is rotated around the axis x, as in the elliptical column processing step. Then, the irradiation position (focal position s) of the laser beam L is moved in accordance with the rotational phase of the processed outer peripheral shape that moves with the rotation.
Next, the phase for forming the rake face is obtained, and the gash and the rake face 15 are formed on the cylindrical material 20 that has been subjected to the outer diameter machining, thereby forming the gash and the rake face 15 and the side blade 12. And the ball blade 13 is formed (cutting blade processing step), and the ball end mill 1 is manufactured.

  When the workpiece (not shown) is cut using the ball end mill 1 configured as described above, the shank portion 3 is held on the spindle of the machine tool (not shown) and rotated around the axis x. Is done. Then, the workpiece can be cut by the cutting edge portion 11 by feeding the ball end mill 1 in the direction intersecting the axis x or in the direction of the axis x by the main shaft.

In the present embodiment, the outer peripheral portion 21 of the tool tip portion 2 is formed by an elliptical column portion 31 and a tip ball portion 32, and the outer diameter of the cutting edge portion 11 is set to an ellipse major axis b, and the outermost periphery of the ellipse Side blades 12 and ball blades 13 are formed in the part. For this reason, when processing the workpiece, the side blades 12 or the ball blades 13 first contact the workpiece, and the outer peripheral portion 21 functions as a flank so as not to contact the workpiece. In addition, in the elliptical column forming step and the tip ball processing step for forming the elliptical column portion 31 on the cylindrical material 20, the elliptical column portion 31 and the tip ball portion 32 that function as the flank of the tool tip portion 2 can be formed. . Therefore, it is not necessary to provide a process of processing the flank separately from the process of processing the outer peripheral portion 21, and the manufacturing process can be simplified.
Further, since the outer peripheral portion 21 formed in an ellipse is formed with a seamless curved surface, chips generated during cutting can be smoothly discharged along the curved surface of the outer peripheral portion 21. Moreover, since chips can be discharged smoothly, cutting resistance can be reduced, and stable cutting performance with a long life can be obtained.

Further, by rotating the shank portion 3 to which the columnar material 20 is attached about the axis x while processing the rotational phase of the elliptical shape e and the irradiation position (focal position s) of the laser beam L, The elliptical shape of the portion 21 can be easily processed.
In addition, high-hardness materials such as cBN sintered bodies, sintered diamonds, and cemented carbides are used as materials for small-diameter end mills used for precision cutting applications. Therefore, it is possible to prevent a decrease in processing accuracy due to deflection or the like caused by processing with a conventional grindstone.
Further, the tool tip portion 2 is formed with a smooth flank in a spheroidal shape with, for example, Rz (maximum height) ≦ 1 μm by laser processing, so that the ball blade 13 can be formed with a sharp ridgeline. Furthermore, since the flank face is similarly smoothly processed into an elliptical column just below the base of the tool from the ball blade 13, the side blade 12 can be formed with a sharp ridgeline, and the ball end mill 1 with high sharpness. Can be manufactured.

The ratio a / b of the minor axis a to the major axis b of the ellipse is set so that the ratio a / b exceeds 0.95 because the shape of the outer peripheral portion 21 approaches a perfect circle as it approaches 1. In this case, the ball end mill 1 and the workpiece are in non-critical contact. The term “non-critical” as used herein means that the portion in contact with the workpiece increases in the vicinity of the side blades 12, and if the ball end mill 1 and the workpiece are in non-critical contact, cutting is performed. Resistance increases. As a result, the tool life is shortened and the machining quality is reduced. Therefore, the ratio a / b is set to 0.95 or less.
Note that the smaller the ratio a / b, the more critically the ball end mill 1 and the workpiece are in contact with each other. However, the thickness of the blade portion acting as the cutting edge portion 11 of the ball end mill 1 is reduced and the strength is ensured. Since it becomes difficult, it is preferable to set the lower limit value according to the required strength. Therefore, the ratio a / b is preferably set to 0.1 or more and 0.9 or less, but is set to a range of 0.4 or more and 0.75 or less in consideration of tool breakage resistance and tool manufacturing. Is more desirable.

  As described above, after the outer diameter of the tool tip 2 is processed, the ball blade 13 is processed. In this case, since the flank is formed by the elliptical shape of the formed tip ball portion, the machining of the flank is not necessary when machining this ball blade. Then, by processing the ball blade 13, a ball end mill having a cutting edge portion 11 in which the side blade 12 and the arc-shaped ball blade 13 are continuous is manufactured.

In addition, this invention is not limited to the said embodiment, A various change can be added in the range which does not deviate from the meaning of this invention.
For example, in the above embodiment, the entire tool tip 2 is formed by laser processing. However, other than the elliptical processing step of the outer peripheral portion 21, for example, processing of the gash and the rake face 15 can be performed by grinding.
Moreover, in the said embodiment, after forming the elliptical column part 31 by the elliptical column formation process, it was supposed to perform the front end ball processing process for forming the front end ball part 32. It is good also as performing an ellipse formation process after performing a tip ball processing process.

DESCRIPTION OF SYMBOLS 1 Radius end mill 2 Tool tip part 3 Shank part 4 Neck part 5 Tip part 6 Cemented carbide part 11 Cutting blade part 12 Side blade 13 Ball blade 14 Corner blade 15 Gash and rake face 20 Cylindrical material 21 Outer peripheral part 22 Laser light irradiation mechanism 23 rotating mechanism 24 moving mechanism 24x x-axis stage unit 24y y-axis stage unit 24z z-axis stage unit 25 control unit 26 laser light source 27 galvano scanner 31 elliptical column unit 32 tip ball unit 100 laser processing apparatus L laser beam

Claims (2)

  A pair of cutting blade portions each including a side blade disposed on the outer periphery of the tool tip portion and an arc-shaped ball blade disposed at the tip of the tool tip portion are provided on the tool tip portion rotated about the axis. The tool tip is formed on opposite sides of the axis, and the outer periphery of the tool tip is formed by an ellipse formed by an ellipse around the axis, and the ellipse is provided continuously at the tip of the ellipse. And a tip ball portion formed by a rotating ellipse shape with a minor axis of the ellipse as a rotation axis. The cutting blade portion has the side blades disposed along the axis at both ends of the major axis of the ellipse. A blade is disposed on the surface of the tip ball portion from the tip of the side blade inward along the major axis direction of the ellipse, and the ellipse has a major axis of 2 mm or less and a ratio of minor axis to major axis of 0. .Bo characterized by being set to 95 or less End mill.   A method for producing a ball end mill according to claim 1, wherein an elliptical column processing step for forming an elliptical column portion on a cylindrical material, a tip ball processing step for forming a tip ball portion on the columnar material, and the ellipse A cutting edge forming step for forming a gash and a rake face on the cylindrical material after the column processing step and the tip ball processing step, and forming a side blade and a ball blade, and the elliptical column processing step and the tip ball processing step In the state where the cylindrical material is rotated around its axis, the cylindrical material is irradiated with a laser beam from the tangential direction of the elliptical shape, and is adjusted in accordance with the rotational phase of the elliptical shape that moves with the rotation. A method of manufacturing a ball end mill, wherein the irradiation position of the laser beam is moved.

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